[ViewVC] Diff of: cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC vs.
Revision 1.140 by root, Thu Mar 22 23:47:01 2012 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent::MP - multi-processing/message-passing framework	3	AnyEvent::MP - erlang-style multi-processing/message-passing framework
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
30	rcv $port, pong => sub { warn "pong received\n" };	30	rcv $port, pong => sub { warn "pong received\n" };
31		31
32	# create a port on another node	32	# create a port on another node
33	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
34		34
		35	# destroy a port again
		36	kil $port; # "normal" kill
		37	kil $port, my_error => "everything is broken"; # error kill
		38
35	# monitoring	39	# monitoring
36	mon $port, $cb->(@msg) # callback is invoked on death	40	mon $port, $cb->(@msg) # callback is invoked on death
37	mon $port, $otherport # kill otherport on abnormal death	41	mon $port, $localport # kill localport on abnormal death
38	mon $port, $otherport, @msg # send message on death	42	mon $port, $localport, @msg # send message on death
39		43
40	=head1 CURRENT STATUS	44	# temporarily execute code in port context
		45	peval $port, sub { die "kill the port!" };
41		46
42	bin/aemp - stable.	47	# execute callbacks in $SELF port context
43	AnyEvent::MP - stable API, should work.	48	my $timer = AE::timer 1, 0, psub {
44	AnyEvent::MP::Intro - uptodate, but incomplete.	49	die "kill the port, delayed";
45	AnyEvent::MP::Kernel - mostly stable.	50	};
46	AnyEvent::MP::Global - stable API, protocol not yet final.
47
48	stay tuned.
49		51
50	=head1 DESCRIPTION	52	=head1 DESCRIPTION
51		53
52	This module (-family) implements a simple message passing framework.	54	This module (-family) implements a simple message passing framework.
53		55
…		…
55	on the same or other hosts, and you can supervise entities remotely.	57	on the same or other hosts, and you can supervise entities remotely.
56		58
57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
58	manual page and the examples under F<eg/>.	60	manual page and the examples under F<eg/>.
59		61
60	At the moment, this module family is a bit underdocumented.
61
62	=head1 CONCEPTS	62	=head1 CONCEPTS
63		63
64	=over 4	64	=over 4
65		65
66	=item port	66	=item port
67		67
68	A port is something you can send messages to (with the C<snd> function).	68	Not to be confused with a TCP port, a "port" is something you can send
		69	messages to (with the C<snd> function).
69		70
70	Ports allow you to register C<rcv> handlers that can match all or just	71	Ports allow you to register C<rcv> handlers that can match all or just
71	some messages. Messages send to ports will not be queued, regardless of	72	some messages. Messages send to ports will not be queued, regardless of
72	anything was listening for them or not.	73	anything was listening for them or not.
73		74
		75	Ports are represented by (printable) strings called "port IDs".
		76
74	=item port ID - C<nodeid#portname>	77	=item port ID - C<nodeid#portname>
75		78
76	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as	79	A port ID is the concatenation of a node ID, a hash-mark (C<#>)
77	separator, and a port name (a printable string of unspecified format).	80	as separator, and a port name (a printable string of unspecified
		81	format created by AnyEvent::MP).
78		82
79	=item node	83	=item node
80		84
81	A node is a single process containing at least one port - the node port,	85	A node is a single process containing at least one port - the node port,
82	which enables nodes to manage each other remotely, and to create new	86	which enables nodes to manage each other remotely, and to create new
83	ports.	87	ports.
84		88
85	Nodes are either public (have one or more listening ports) or private	89	Nodes are either public (have one or more listening ports) or private
86	(no listening ports). Private nodes cannot talk to other private nodes	90	(no listening ports). Private nodes cannot talk to other private nodes
87	currently.	91	currently, but all nodes can talk to public nodes.
88		92
		93	Nodes is represented by (printable) strings called "node IDs".
		94
89	=item node ID - C<[a-za-Z0-9_\-.:]+>	95	=item node ID - C<[A-Za-z0-9_\-.:]*>
90		96
91	A node ID is a string that uniquely identifies the node within a	97	A node ID is a string that uniquely identifies the node within a
92	network. Depending on the configuration used, node IDs can look like a	98	network. Depending on the configuration used, node IDs can look like a
93	hostname, a hostname and a port, or a random string. AnyEvent::MP itself	99	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
94	doesn't interpret node IDs in any way.	100	doesn't interpret node IDs in any way except to uniquely identify a node.
95		101
96	=item binds - C<ip:port>	102	=item binds - C<ip:port>
97		103
98	Nodes can only talk to each other by creating some kind of connection to	104	Nodes can only talk to each other by creating some kind of connection to
99	each other. To do this, nodes should listen on one or more local transport	105	each other. To do this, nodes should listen on one or more local transport
		106	endpoints - binds.
		107
100	endpoints - binds. Currently, only standard C<ip:port> specifications can	108	Currently, only standard C<ip:port> specifications can be used, which
101	be used, which specify TCP ports to listen on.	109	specify TCP ports to listen on. So a bind is basically just a tcp socket
		110	in listening mode thta accepts conenctions form other nodes.
102		111
		112	=item seed nodes
		113
		114	When a node starts, it knows nothing about the network it is in - it
		115	needs to connect to at least one other node that is already in the
		116	network. These other nodes are called "seed nodes".
		117
		118	Seed nodes themselves are not special - they are seed nodes only because
		119	some other node I<uses> them as such, but any node can be used as seed
		120	node for other nodes, and eahc node cna use a different set of seed nodes.
		121
		122	In addition to discovering the network, seed nodes are also used to
		123	maintain the network - all nodes using the same seed node form are part of
		124	the same network. If a network is split into multiple subnets because e.g.
		125	the network link between the parts goes down, then using the same seed
		126	nodes for all nodes ensures that eventually the subnets get merged again.
		127
		128	Seed nodes are expected to be long-running, and at least one seed node
		129	should always be available. They should also be relatively responsive - a
		130	seed node that blocks for long periods will slow down everybody else.
		131
		132	For small networks, it's best if every node uses the same set of seed
		133	nodes. For large networks, it can be useful to specify "regional" seed
		134	nodes for most nodes in an area, and use all seed nodes as seed nodes for
		135	each other. What's important is that all seed nodes connections form a
		136	complete graph, so that the network cannot split into separate subnets
		137	forever.
		138
		139	Seed nodes are represented by seed IDs.
		140
103	=item seeds - C<host:port>	141	=item seed IDs - C<host:port>
104		142
105	When a node starts, it knows nothing about the network. To teach the node	143	Seed IDs are transport endpoint(s) (usually a hostname/IP address and a
106	about the network it first has to contact some other node within the	144	TCP port) of nodes that should be used as seed nodes.
107	network. This node is called a seed.
108		145
109	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes	146	=item global nodes
110	are expected to be long-running, and at least one of those should always
111	be available. When nodes run out of connections (e.g. due to a network
112	error), they try to re-establish connections to some seednodes again to
113	join the network.
114		147
115	Apart from being sued for seeding, seednodes are not special in any way -	148	An AEMP network needs a discovery service - nodes need to know how to
116	every public node can be a seednode.	149	connect to other nodes they only know by name. In addition, AEMP offers a
		150	distributed "group database", which maps group names to a list of strings
		151	- for example, to register worker ports.
		152
		153	A network needs at least one global node to work, and allows every node to
		154	be a global node.
		155
		156	Any node that loads the L<AnyEvent::MP::Global> module becomes a global
		157	node and tries to keep connections to all other nodes. So while it can
		158	make sense to make every node "global" in small networks, it usually makes
		159	sense to only make seed nodes into global nodes in large networks (nodes
		160	keep connections to seed nodes and global nodes, so makign them the same
		161	reduces overhead).
117		162
118	=back	163	=back
119		164
120	=head1 VARIABLES/FUNCTIONS	165	=head1 VARIABLES/FUNCTIONS
121		166
…		…
123		168
124	=cut	169	=cut
125		170
126	package AnyEvent::MP;	171	package AnyEvent::MP;
127		172
		173	use AnyEvent::MP::Config ();
128	use AnyEvent::MP::Kernel;	174	use AnyEvent::MP::Kernel;
		175	use AnyEvent::MP::Kernel qw(%NODE %PORT %PORT_DATA $UNIQ $RUNIQ $ID);
129		176
130	use common::sense;	177	use common::sense;
131		178
132	use Carp ();	179	use Carp ();
133		180
134	use AE ();	181	use AE ();
		182	use Guard ();
135		183
136	use base "Exporter";	184	use base "Exporter";
137		185
138	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	186	our $VERSION = $AnyEvent::MP::Config::VERSION;
139		187
140	our @EXPORT = qw(	188	our @EXPORT = qw(
141	NODE $NODE *SELF node_of after	189	NODE $NODE *SELF node_of after
142	configure	190	configure
143	snd rcv mon mon_guard kil reg psub spawn	191	snd rcv mon mon_guard kil psub peval spawn cal
144	port	192	port
		193	db_set db_del db_reg
		194	db_mon db_family db_keys db_values
145	);	195	);
146		196
147	our $SELF;	197	our $SELF;
148		198
149	sub _self_die() {	199	sub _self_die() {
…		…
160		210
161	=item $nodeid = node_of $port	211	=item $nodeid = node_of $port
162		212
163	Extracts and returns the node ID from a port ID or a node ID.	213	Extracts and returns the node ID from a port ID or a node ID.
164		214
		215	=item configure $profile, key => value...
		216
165	=item configure key => value...	217	=item configure key => value...
166		218
167	Before a node can talk to other nodes on the network (i.e. enter	219	Before a node can talk to other nodes on the network (i.e. enter
168	"distributed mode") it has to configure itself - the minimum a node needs	220	"distributed mode") it has to configure itself - the minimum a node needs
169	to know is its own name, and optionally it should know the addresses of	221	to know is its own name, and optionally it should know the addresses of
170	some other nodes in the network to discover other nodes.	222	some other nodes in the network to discover other nodes.
171		223
172	This function configures a node - it must be called exactly once (or	224	This function configures a node - it must be called exactly once (or
173	never) before calling other AnyEvent::MP functions.	225	never) before calling other AnyEvent::MP functions.
174		226
		227	The key/value pairs are basically the same ones as documented for the
		228	F<aemp> command line utility (sans the set/del prefix), with these additions:
		229
		230	=over 4
		231
		232	=item norc => $boolean (default false)
		233
		234	If true, then the rc file (e.g. F<~/.perl-anyevent-mp>) will I<not>
		235	be consulted - all configuraiton options must be specified in the
		236	C<configure> call.
		237
		238	=item force => $boolean (default false)
		239
		240	IF true, then the values specified in the C<configure> will take
		241	precedence over any values configured via the rc file. The default is for
		242	the rc file to override any options specified in the program.
		243
		244	=item secure => $pass->(@msg)
		245
		246	In addition to specifying a boolean, you can specify a code reference that
		247	is called for every code execution attempt - the execution request is
		248	granted iff the callback returns a true value.
		249
		250	Most of the time the callback should look only at
		251	C<$AnyEvent::MP::Kernel::SRCNODE> to make a decision, and not at the
		252	actual message (which can be about anything, and is mostly provided for
		253	diagnostic purposes).
		254
		255	See F<semp setsecure> for more info.
		256
		257	=back
		258
175	=over 4	259	=over 4
176		260
177	=item step 1, gathering configuration from profiles	261	=item step 1, gathering configuration from profiles
178		262
179	The function first looks up a profile in the aemp configuration (see the	263	The function first looks up a profile in the aemp configuration (see the
180	L<aemp> commandline utility). The profile name can be specified via the	264	L<aemp> commandline utility). The profile name can be specified via the
181	named C<profile> parameter. If it is missing, then the nodename (F<uname	265	named C<profile> parameter or can simply be the first parameter). If it is
182	-n>) will be used as profile name.	266	missing, then the nodename (F<uname -n>) will be used as profile name.
183		267
184	The profile data is then gathered as follows:	268	The profile data is then gathered as follows:
185		269
186	First, all remaining key => value pairs (all of which are conviniently	270	First, all remaining key => value pairs (all of which are conveniently
187	undocumented at the moment) will be interpreted as configuration	271	undocumented at the moment) will be interpreted as configuration
188	data. Then they will be overwritten by any values specified in the global	272	data. Then they will be overwritten by any values specified in the global
189	default configuration (see the F<aemp> utility), then the chain of	273	default configuration (see the F<aemp> utility), then the chain of
190	profiles chosen by the profile name (and any C<parent> attributes).	274	profiles chosen by the profile name (and any C<parent> attributes).
191		275
192	That means that the values specified in the profile have highest priority	276	That means that the values specified in the profile have highest priority
193	and the values specified directly via C<configure> have lowest priority,	277	and the values specified directly via C<configure> have lowest priority,
194	and can only be used to specify defaults.	278	and can only be used to specify defaults.
195		279
196	If the profile specifies a node ID, then this will become the node ID of	280	If the profile specifies a node ID, then this will become the node ID of
197	this process. If not, then the profile name will be used as node ID. The	281	this process. If not, then the profile name will be used as node ID, with
198	special node ID of C<anon/> will be replaced by a random node ID.	282	a unique randoms tring (C</%u>) appended.
		283
		284	The node ID can contain some C<%> sequences that are expanded: C<%n>
		285	is expanded to the local nodename, C<%u> is replaced by a random
		286	strign to make the node unique. For example, the F<aemp> commandline
		287	utility uses C<aemp/%n/%u> as nodename, which might expand to
		288	C<aemp/cerebro/ZQDGSIkRhEZQDGSIkRhE>.
199		289
200	=item step 2, bind listener sockets	290	=item step 2, bind listener sockets
201		291
202	The next step is to look up the binds in the profile, followed by binding	292	The next step is to look up the binds in the profile, followed by binding
203	aemp protocol listeners on all binds specified (it is possible and valid	293	aemp protocol listeners on all binds specified (it is possible and valid
…		…
209	used, meaning the node will bind on a dynamically-assigned port on every	299	used, meaning the node will bind on a dynamically-assigned port on every
210	local IP address it finds.	300	local IP address it finds.
211		301
212	=item step 3, connect to seed nodes	302	=item step 3, connect to seed nodes
213		303
214	As the last step, the seeds list from the profile is passed to the	304	As the last step, the seed ID list from the profile is passed to the
215	L<AnyEvent::MP::Global> module, which will then use it to keep	305	L<AnyEvent::MP::Global> module, which will then use it to keep
216	connectivity with at least one node at any point in time.	306	connectivity with at least one node at any point in time.
217		307
218	=back	308	=back
219		309
220	Example: become a distributed node using the locla node name as profile.	310	Example: become a distributed node using the local node name as profile.
221	This should be the most common form of invocation for "daemon"-type nodes.	311	This should be the most common form of invocation for "daemon"-type nodes.
222		312
223	configure	313	configure
224		314
225	Example: become an anonymous node. This form is often used for commandline	315	Example: become a semi-anonymous node. This form is often used for
226	clients.	316	commandline clients.
227		317
228	configure nodeid => "anon/";	318	configure nodeid => "myscript/%n/%u";
229		319
230	Example: configure a node using a profile called seed, which si suitable	320	Example: configure a node using a profile called seed, which is suitable
231	for a seed node as it binds on all local addresses on a fixed port (4040,	321	for a seed node as it binds on all local addresses on a fixed port (4040,
232	customary for aemp).	322	customary for aemp).
233		323
234	# use the aemp commandline utility	324	# use the aemp commandline utility
235	# aemp profile seed nodeid anon/ binds '*:4040'	325	# aemp profile seed binds '*:4040'
236		326
237	# then use it	327	# then use it
238	configure profile => "seed";	328	configure profile => "seed";
239		329
240	# or simply use aemp from the shell again:	330	# or simply use aemp from the shell again:
…		…
305		395
306	=cut	396	=cut
307		397
308	sub rcv($@);	398	sub rcv($@);
309		399
310	sub _kilme {	400	my $KILME = sub {
311	die "received message on port without callback";	401	(my $tag = substr $_[0], 0, 30) =~ s/([\x20-\x7e])/./g;
312	}	402	kil $SELF, unhandled_message => "no callback found for message '$tag'";
		403	};
313		404
314	sub port(;&) {	405	sub port(;&) {
315	my $id = "$UNIQ." . $ID++;	406	my $id = $UNIQ . ++$ID;
316	my $port = "$NODE#$id";	407	my $port = "$NODE#$id";
317		408
318	rcv $port, shift \|\| \&_kilme;	409	rcv $port, shift \|\| $KILME;
319		410
320	$port	411	$port
321	}	412	}
322		413
323	=item rcv $local_port, $callback->(@msg)	414	=item rcv $local_port, $callback->(@msg)
…		…
328		419
329	The global C<$SELF> (exported by this module) contains C<$port> while	420	The global C<$SELF> (exported by this module) contains C<$port> while
330	executing the callback. Runtime errors during callback execution will	421	executing the callback. Runtime errors during callback execution will
331	result in the port being C<kil>ed.	422	result in the port being C<kil>ed.
332		423
333	The default callback received all messages not matched by a more specific	424	The default callback receives all messages not matched by a more specific
334	C<tag> match.	425	C<tag> match.
335		426
336	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	427	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
337		428
338	Register (or replace) callbacks to be called on messages starting with the	429	Register (or replace) callbacks to be called on messages starting with the
…		…
359	msg1 => sub { ... },	450	msg1 => sub { ... },
360	...	451	...
361	;	452	;
362		453
363	Example: temporarily register a rcv callback for a tag matching some port	454	Example: temporarily register a rcv callback for a tag matching some port
364	(e.g. for a rpc reply) and unregister it after a message was received.	455	(e.g. for an rpc reply) and unregister it after a message was received.
365		456
366	rcv $port, $otherport => sub {	457	rcv $port, $otherport => sub {
367	my @reply = @_;	458	my @reply = @_;
368		459
369	rcv $SELF, $otherport;	460	rcv $SELF, $otherport;
…		…
382	if (ref $_[0]) {	473	if (ref $_[0]) {
383	if (my $self = $PORT_DATA{$portid}) {	474	if (my $self = $PORT_DATA{$portid}) {
384	"AnyEvent::MP::Port" eq ref $self	475	"AnyEvent::MP::Port" eq ref $self
385	or Carp::croak "$port: rcv can only be called on message matching ports, caught";	476	or Carp::croak "$port: rcv can only be called on message matching ports, caught";
386		477
387	$self->[2] = shift;	478	$self->[0] = shift;
388	} else {	479	} else {
389	my $cb = shift;	480	my $cb = shift;
390	$PORT{$portid} = sub {	481	$PORT{$portid} = sub {
391	local $SELF = $port;	482	local $SELF = $port;
392	eval { &$cb }; _self_die if $@;	483	eval { &$cb }; _self_die if $@;
393	};	484	};
394	}	485	}
395	} elsif (defined $_[0]) {	486	} elsif (defined $_[0]) {
396	my $self = $PORT_DATA{$portid} \|\|= do {	487	my $self = $PORT_DATA{$portid} \|\|= do {
397	my $self = bless [$PORT{$port} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";	488	my $self = bless [$PORT{$portid} \|\| sub { }, { }, $port], "AnyEvent::MP::Port";
398		489
399	$PORT{$portid} = sub {	490	$PORT{$portid} = sub {
400	local $SELF = $port;	491	local $SELF = $port;
401		492
402	if (my $cb = $self->[1]{$_[0]}) {	493	if (my $cb = $self->[1]{$_[0]}) {
…		…
424	}	515	}
425		516
426	$port	517	$port
427	}	518	}
428		519
		520	=item peval $port, $coderef[, @args]
		521
		522	Evaluates the given C<$codref> within the contetx of C<$port>, that is,
		523	when the code throews an exception the C<$port> will be killed.
		524
		525	Any remaining args will be passed to the callback. Any return values will
		526	be returned to the caller.
		527
		528	This is useful when you temporarily want to execute code in the context of
		529	a port.
		530
		531	Example: create a port and run some initialisation code in it's context.
		532
		533	my $port = port { ... };
		534
		535	peval $port, sub {
		536	init
		537	or die "unable to init";
		538	};
		539
		540	=cut
		541
		542	sub peval($$) {
		543	local $SELF = shift;
		544	my $cb = shift;
		545
		546	if (wantarray) {
		547	my @res = eval { &$cb };
		548	_self_die if $@;
		549	@res
		550	} else {
		551	my $res = eval { &$cb };
		552	_self_die if $@;
		553	$res
		554	}
		555	}
		556
429	=item $closure = psub { BLOCK }	557	=item $closure = psub { BLOCK }
430		558
431	Remembers C<$SELF> and creates a closure out of the BLOCK. When the	559	Remembers C<$SELF> and creates a closure out of the BLOCK. When the
432	closure is executed, sets up the environment in the same way as in C<rcv>	560	closure is executed, sets up the environment in the same way as in C<rcv>
433	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.	561	callbacks, i.e. runtime errors will cause the port to get C<kil>ed.
		562
		563	The effect is basically as if it returned C<< sub { peval $SELF, sub {
		564	BLOCK }, @_ } >>.
434		565
435	This is useful when you register callbacks from C<rcv> callbacks:	566	This is useful when you register callbacks from C<rcv> callbacks:
436		567
437	rcv delayed_reply => sub {	568	rcv delayed_reply => sub {
438	my ($delay, @reply) = @_;	569	my ($delay, @reply) = @_;
…		…
462	$res	593	$res
463	}	594	}
464	}	595	}
465	}	596	}
466		597
		598	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
		599
		600	=item $guard = mon $port # kill $SELF when $port dies
		601
467	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies	602	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
468
469	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
470
471	=item $guard = mon $port # kill $SELF when $port dies
472		603
473	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies	604	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
474		605
475	Monitor the given port and do something when the port is killed or	606	Monitor the given port and do something when the port is killed or
476	messages to it were lost, and optionally return a guard that can be used	607	messages to it were lost, and optionally return a guard that can be used
477	to stop monitoring again.	608	to stop monitoring again.
		609
		610	The first two forms distinguish between "normal" and "abnormal" kil's:
		611
		612	In the first form (another port given), if the C<$port> is C<kil>'ed with
		613	a non-empty reason, the other port (C<$rcvport>) will be kil'ed with the
		614	same reason. That is, on "normal" kil's nothing happens, while under all
		615	other conditions, the other port is killed with the same reason.
		616
		617	The second form (kill self) is the same as the first form, except that
		618	C<$rvport> defaults to C<$SELF>.
		619
		620	The remaining forms don't distinguish between "normal" and "abnormal" kil's
		621	- it's up to the callback or receiver to check whether the C<@reason> is
		622	empty and act accordingly.
		623
		624	In the third form (callback), the callback is simply called with any
		625	number of C<@reason> elements (empty @reason means that the port was deleted
		626	"normally"). Note also that I<< the callback B<must> never die >>, so use
		627	C<eval> if unsure.
		628
		629	In the last form (message), a message of the form C<$rcvport, @msg,
		630	@reason> will be C<snd>.
		631
		632	Monitoring-actions are one-shot: once messages are lost (and a monitoring
		633	alert was raised), they are removed and will not trigger again, even if it
		634	turns out that the port is still alive.
		635
		636	As a rule of thumb, monitoring requests should always monitor a remote
		637	port locally (using a local C<$rcvport> or a callback). The reason is that
		638	kill messages might get lost, just like any other message. Another less
		639	obvious reason is that even monitoring requests can get lost (for example,
		640	when the connection to the other node goes down permanently). When
		641	monitoring a port locally these problems do not exist.
478		642
479	C<mon> effectively guarantees that, in the absence of hardware failures,	643	C<mon> effectively guarantees that, in the absence of hardware failures,
480	after starting the monitor, either all messages sent to the port will	644	after starting the monitor, either all messages sent to the port will
481	arrive, or the monitoring action will be invoked after possible message	645	arrive, or the monitoring action will be invoked after possible message
482	loss has been detected. No messages will be lost "in between" (after	646	loss has been detected. No messages will be lost "in between" (after
483	the first lost message no further messages will be received by the	647	the first lost message no further messages will be received by the
484	port). After the monitoring action was invoked, further messages might get	648	port). After the monitoring action was invoked, further messages might get
485	delivered again.	649	delivered again.
486		650
487	Note that monitoring-actions are one-shot: once messages are lost (and a	651	Inter-host-connection timeouts and monitoring depend on the transport
488	monitoring alert was raised), they are removed and will not trigger again.	652	used. The only transport currently implemented is TCP, and AnyEvent::MP
		653	relies on TCP to detect node-downs (this can take 10-15 minutes on a
		654	non-idle connection, and usually around two hours for idle connections).
489		655
490	In the first form (callback), the callback is simply called with any	656	This means that monitoring is good for program errors and cleaning up
491	number of C<@reason> elements (no @reason means that the port was deleted	657	stuff eventually, but they are no replacement for a timeout when you need
492	"normally"). Note also that I<< the callback B<must> never die >>, so use	658	to ensure some maximum latency.
493	C<eval> if unsure.
494
495	In the second form (another port given), the other port (C<$rcvport>)
496	will be C<kil>'ed with C<@reason>, iff a @reason was specified, i.e. on
497	"normal" kils nothing happens, while under all other conditions, the other
498	port is killed with the same reason.
499
500	The third form (kill self) is the same as the second form, except that
501	C<$rvport> defaults to C<$SELF>.
502
503	In the last form (message), a message of the form C<@msg, @reason> will be
504	C<snd>.
505
506	As a rule of thumb, monitoring requests should always monitor a port from
507	a local port (or callback). The reason is that kill messages might get
508	lost, just like any other message. Another less obvious reason is that
509	even monitoring requests can get lost (for exmaple, when the connection
510	to the other node goes down permanently). When monitoring a port locally
511	these problems do not exist.
512		659
513	Example: call a given callback when C<$port> is killed.	660	Example: call a given callback when C<$port> is killed.
514		661
515	mon $port, sub { warn "port died because of <@_>\n" };	662	mon $port, sub { warn "port died because of <@_>\n" };
516		663
…		…
544	}	691	}
545		692
546	$node->monitor ($port, $cb);	693	$node->monitor ($port, $cb);
547		694
548	defined wantarray	695	defined wantarray
549	and AnyEvent::Util::guard { $node->unmonitor ($port, $cb) }	696	and ($cb += 0, Guard::guard { $node->unmonitor ($port, $cb) })
550	}	697	}
551		698
552	=item $guard = mon_guard $port, $ref, $ref...	699	=item $guard = mon_guard $port, $ref, $ref...
553		700
554	Monitors the given C<$port> and keeps the passed references. When the port	701	Monitors the given C<$port> and keeps the passed references. When the port
…		…
577		724
578	=item kil $port[, @reason]	725	=item kil $port[, @reason]
579		726
580	Kill the specified port with the given C<@reason>.	727	Kill the specified port with the given C<@reason>.
581		728
582	If no C<@reason> is specified, then the port is killed "normally" (ports	729	If no C<@reason> is specified, then the port is killed "normally" -
583	monitoring other ports will not necessarily die because a port dies	730	monitor callback will be invoked, but the kil will not cause linked ports
584	"normally").	731	(C<mon $mport, $lport> form) to get killed.
585		732
586	Otherwise, linked ports get killed with the same reason (second form of	733	If a C<@reason> is specified, then linked ports (C<mon $mport, $lport>
587	C<mon>, see above).	734	form) get killed with the same reason.
588		735
589	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	736	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
590	will be reported as reason C<< die => $@ >>.	737	will be reported as reason C<< die => $@ >>.
591		738
592	Transport/communication errors are reported as C<< transport_error =>	739	Transport/communication errors are reported as C<< transport_error =>
593	$message >>.	740	$message >>.
594		741
595	=cut	742	Common idioms:
		743
		744	# silently remove yourself, do not kill linked ports
		745	kil $SELF;
		746
		747	# report a failure in some detail
		748	kil $SELF, failure_mode_1 => "it failed with too high temperature";
		749
		750	# do not waste much time with killing, just die when something goes wrong
		751	open my $fh, "<file"
		752	or die "file: $!";
596		753
597	=item $port = spawn $node, $initfunc[, @initdata]	754	=item $port = spawn $node, $initfunc[, @initdata]
598		755
599	Creates a port on the node C<$node> (which can also be a port ID, in which	756	Creates a port on the node C<$node> (which can also be a port ID, in which
600	case it's the node where that port resides).	757	case it's the node where that port resides).
…		…
611	the package, then the package above the package and so on (e.g.	768	the package, then the package above the package and so on (e.g.
612	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	769	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
613	exists or it runs out of package names.	770	exists or it runs out of package names.
614		771
615	The init function is then called with the newly-created port as context	772	The init function is then called with the newly-created port as context
616	object (C<$SELF>) and the C<@initdata> values as arguments.	773	object (C<$SELF>) and the C<@initdata> values as arguments. It I<must>
		774	call one of the C<rcv> functions to set callbacks on C<$SELF>, otherwise
		775	the port might not get created.
617		776
618	A common idiom is to pass a local port, immediately monitor the spawned	777	A common idiom is to pass a local port, immediately monitor the spawned
619	port, and in the remote init function, immediately monitor the passed	778	port, and in the remote init function, immediately monitor the passed
620	local port. This two-way monitoring ensures that both ports get cleaned up	779	local port. This two-way monitoring ensures that both ports get cleaned up
621	when there is a problem.	780	when there is a problem.
622		781
		782	C<spawn> guarantees that the C<$initfunc> has no visible effects on the
		783	caller before C<spawn> returns (by delaying invocation when spawn is
		784	called for the local node).
		785
623	Example: spawn a chat server port on C<$othernode>.	786	Example: spawn a chat server port on C<$othernode>.
624		787
625	# this node, executed from within a port context:	788	# this node, executed from within a port context:
626	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	789	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
627	mon $server;	790	mon $server;
…		…
641		804
642	sub _spawn {	805	sub _spawn {
643	my $port = shift;	806	my $port = shift;
644	my $init = shift;	807	my $init = shift;
645		808
		809	# rcv will create the actual port
646	local $SELF = "$NODE#$port";	810	local $SELF = "$NODE#$port";
647	eval {	811	eval {
648	&{ load_func $init }	812	&{ load_func $init }
649	};	813	};
650	_self_die if $@;	814	_self_die if $@;
651	}	815	}
652		816
653	sub spawn(@) {	817	sub spawn(@) {
654	my ($nodeid, undef) = split /#/, shift, 2;	818	my ($nodeid, undef) = split /#/, shift, 2;
655		819
656	my $id = "$RUNIQ." . $ID++;	820	my $id = $RUNIQ . ++$ID;
657		821
658	$_[0] =~ /::/	822	$_[0] =~ /::/
659	or Carp::croak "spawn init function must be a fully-qualified name, caught";	823	or Carp::croak "spawn init function must be a fully-qualified name, caught";
660		824
661	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;	825	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
662		826
663	"$nodeid#$id"	827	"$nodeid#$id"
664	}	828	}
		829
665		830
666	=item after $timeout, @msg	831	=item after $timeout, @msg
667		832
668	=item after $timeout, $callback	833	=item after $timeout, $callback
669		834
…		…
685	? $action[0]()	850	? $action[0]()
686	: snd @action;	851	: snd @action;
687	};	852	};
688	}	853	}
689		854
		855	#=item $cb2 = timeout $seconds, $cb[, @args]
		856
		857	=item cal $port, @msg, $callback[, $timeout]
		858
		859	A simple form of RPC - sends a message to the given C<$port> with the
		860	given contents (C<@msg>), but adds a reply port to the message.
		861
		862	The reply port is created temporarily just for the purpose of receiving
		863	the reply, and will be C<kil>ed when no longer needed.
		864
		865	A reply message sent to the port is passed to the C<$callback> as-is.
		866
		867	If an optional time-out (in seconds) is given and it is not C<undef>,
		868	then the callback will be called without any arguments after the time-out
		869	elapsed and the port is C<kil>ed.
		870
		871	If no time-out is given (or it is C<undef>), then the local port will
		872	monitor the remote port instead, so it eventually gets cleaned-up.
		873
		874	Currently this function returns the temporary port, but this "feature"
		875	might go in future versions unless you can make a convincing case that
		876	this is indeed useful for something.
		877
		878	=cut
		879
		880	sub cal(@) {
		881	my $timeout = ref $_[-1] ? undef : pop;
		882	my $cb = pop;
		883
		884	my $port = port {
		885	undef $timeout;
		886	kil $SELF;
		887	&$cb;
		888	};
		889
		890	if (defined $timeout) {
		891	$timeout = AE::timer $timeout, 0, sub {
		892	undef $timeout;
		893	kil $port;
		894	$cb->();
		895	};
		896	} else {
		897	mon $_[0], sub {
		898	kil $port;
		899	$cb->();
		900	};
		901	}
		902
		903	push @_, $port;
		904	&snd;
		905
		906	$port
		907	}
		908
		909	=back
		910
		911	=head1 DISTRIBUTED DATABASE
		912
		913	AnyEvent::MP comes with a simple distributed database. The database will
		914	be mirrored asynchronously on all global nodes. Other nodes bind to one
		915	of the global nodes for their needs. Every node has a "local database"
		916	which contains all the values that are set locally. All local databases
		917	are merged together to form the global database, which can be queried.
		918
		919	The database structure is that of a two-level hash - the database hash
		920	contains hashes which contain values, similarly to a perl hash of hashes,
		921	i.e.:
		922
		923	$DATABASE{$family}{$subkey} = $value
		924
		925	The top level hash key is called "family", and the second-level hash key
		926	is called "subkey" or simply "key".
		927
		928	The family must be alphanumeric, i.e. start with a letter and consist
		929	of letters, digits, underscores and colons (C<[A-Za-z][A-Za-z0-9_:]*>,
		930	pretty much like Perl module names.
		931
		932	As the family namespace is global, it is recommended to prefix family names
		933	with the name of the application or module using it.
		934
		935	The subkeys must be non-empty strings, with no further restrictions.
		936
		937	The values should preferably be strings, but other perl scalars should
		938	work as well (such as C<undef>, arrays and hashes).
		939
		940	Every database entry is owned by one node - adding the same family/subkey
		941	combination on multiple nodes will not cause discomfort for AnyEvent::MP,
		942	but the result might be nondeterministic, i.e. the key might have
		943	different values on different nodes.
		944
		945	Different subkeys in the same family can be owned by different nodes
		946	without problems, and in fact, this is the common method to create worker
		947	pools. For example, a worker port for image scaling might do this:
		948
		949	db_set my_image_scalers => $port;
		950
		951	And clients looking for an image scaler will want to get the
		952	C<my_image_scalers> keys from time to time:
		953
		954	db_keys my_image_scalers => sub {
		955	@ports = @{ $_[0] };
		956	};
		957
		958	Or better yet, they want to monitor the database family, so they always
		959	have a reasonable up-to-date copy:
		960
		961	db_mon my_image_scalers => sub {
		962	@ports = keys %{ $_[0] };
		963	};
		964
		965	In general, you can set or delete single subkeys, but query and monitor
		966	whole families only.
		967
		968	If you feel the need to monitor or query a single subkey, try giving it
		969	it's own family.
		970
		971	=over
		972
		973	=item $guard = db_set $family => $subkey [=> $value]
		974
		975	Sets (or replaces) a key to the database - if C<$value> is omitted,
		976	C<undef> is used instead.
		977
		978	When called in non-void context, C<db_set> returns a guard that
		979	automatically calls C<db_del> when it is destroyed.
		980
		981	=item db_del $family => $subkey...
		982
		983	Deletes one or more subkeys from the database family.
		984
		985	=item $guard = db_reg $family => $port => $value
		986
		987	=item $guard = db_reg $family => $port
		988
		989	=item $guard = db_reg $family
		990
		991	Registers a port in the given family and optionally returns a guard to
		992	remove it.
		993
		994	This function basically does the same as:
		995
		996	db_set $family => $port => $value
		997
		998	Except that the port is monitored and automatically removed from the
		999	database family when it is kil'ed.
		1000
		1001	If C<$value> is missing, C<undef> is used. If C<$port> is missing, then
		1002	C<$SELF> is used.
		1003
		1004	This function is most useful to register a port in some port group (which
		1005	is just another name for a database family), and have it removed when the
		1006	port is gone. This works best when the port is a local port.
		1007
		1008	=cut
		1009
		1010	sub db_reg($$;$) {
		1011	my $family = shift;
		1012	my $port = @_ ? shift : $SELF;
		1013
		1014	my $clr = sub { db_del $family => $port };
		1015	mon $port, $clr;
		1016
		1017	db_set $family => $port => $_[0];
		1018
		1019	defined wantarray
		1020	and &Guard::guard ($clr)
		1021	}
		1022
		1023	=item db_family $family => $cb->(\%familyhash)
		1024
		1025	Queries the named database C<$family> and call the callback with the
		1026	family represented as a hash. You can keep and freely modify the hash.
		1027
		1028	=item db_keys $family => $cb->(\@keys)
		1029
		1030	Same as C<db_family>, except it only queries the family I<subkeys> and passes
		1031	them as array reference to the callback.
		1032
		1033	=item db_values $family => $cb->(\@values)
		1034
		1035	Same as C<db_family>, except it only queries the family I<values> and passes them
		1036	as array reference to the callback.
		1037
		1038	=item $guard = db_mon $family => $cb->($familyhash, \@added, \@changed, \@deleted)
		1039
		1040	Creates a monitor on the given database family. Each time a key is set
		1041	or or is deleted the callback is called with a hash containing the
		1042	database family and three lists of added, changed and deleted subkeys,
		1043	respectively. If no keys have changed then the array reference might be
		1044	C<undef> or even missing.
		1045
		1046	If not called in void context, a guard object is returned that, when
		1047	destroyed, stops the monitor.
		1048
		1049	The family hash reference and the key arrays belong to AnyEvent::MP and
		1050	B<must not be modified or stored> by the callback. When in doubt, make a
		1051	copy.
		1052
		1053	As soon as possible after the monitoring starts, the callback will be
		1054	called with the intiial contents of the family, even if it is empty,
		1055	i.e. there will always be a timely call to the callback with the current
		1056	contents.
		1057
		1058	It is possible that the callback is called with a change event even though
		1059	the subkey is already present and the value has not changed.
		1060
		1061	The monitoring stops when the guard object is destroyed.
		1062
		1063	Example: on every change to the family "mygroup", print out all keys.
		1064
		1065	my $guard = db_mon mygroup => sub {
		1066	my ($family, $a, $c, $d) = @_;
		1067	print "mygroup members: ", (join " ", keys %$family), "\n";
		1068	};
		1069
		1070	Exmaple: wait until the family "My::Module::workers" is non-empty.
		1071
		1072	my $guard; $guard = db_mon My::Module::workers => sub {
		1073	my ($family, $a, $c, $d) = @_;
		1074	return unless %$family;
		1075	undef $guard;
		1076	print "My::Module::workers now nonempty\n";
		1077	};
		1078
		1079	Example: print all changes to the family "AnyRvent::Fantasy::Module".
		1080
		1081	my $guard = db_mon AnyRvent::Fantasy::Module => sub {
		1082	my ($family, $a, $c, $d) = @_;
		1083
		1084	print "+$_=$family->{$_}\n" for @$a;
		1085	print "*$_=$family->{$_}\n" for @$c;
		1086	print "-$_=$family->{$_}\n" for @$d;
		1087	};
		1088
		1089	=cut
		1090
690	=back	1091	=back
691		1092
692	=head1 AnyEvent::MP vs. Distributed Erlang	1093	=head1 AnyEvent::MP vs. Distributed Erlang
693		1094
694	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node	1095	AnyEvent::MP got lots of its ideas from distributed Erlang (Erlang node
695	== aemp node, Erlang process == aemp port), so many of the documents and	1096	== aemp node, Erlang process == aemp port), so many of the documents and
696	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a	1097	programming techniques employed by Erlang apply to AnyEvent::MP. Here is a
697	sample:	1098	sample:
698		1099
699	http://www.Erlang.se/doc/programming_rules.shtml	1100	http://www.erlang.se/doc/programming_rules.shtml
700	http://Erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4	1101	http://erlang.org/doc/getting_started/part_frame.html # chapters 3 and 4
701	http://Erlang.org/download/Erlang-book-part1.pdf # chapters 5 and 6	1102	http://erlang.org/download/erlang-book-part1.pdf # chapters 5 and 6
702	http://Erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5	1103	http://erlang.org/download/armstrong_thesis_2003.pdf # chapters 4 and 5
703		1104
704	Despite the similarities, there are also some important differences:	1105	Despite the similarities, there are also some important differences:
705		1106
706	=over 4	1107	=over 4
707		1108
708	=item * Node IDs are arbitrary strings in AEMP.	1109	=item * Node IDs are arbitrary strings in AEMP.
709		1110
710	Erlang relies on special naming and DNS to work everywhere in the same	1111	Erlang relies on special naming and DNS to work everywhere in the same
711	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by	1112	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
712	configuraiton or DNS), but will otherwise discover other odes itself.	1113	configuration or DNS), and possibly the addresses of some seed nodes, but
		1114	will otherwise discover other nodes (and their IDs) itself.
713		1115
714	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP	1116	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
715	uses "local ports are like remote ports".	1117	uses "local ports are like remote ports".
716		1118
717	The failure modes for local ports are quite different (runtime errors	1119	The failure modes for local ports are quite different (runtime errors
…		…
726	ports being the special case/exception, where transport errors cannot	1128	ports being the special case/exception, where transport errors cannot
727	occur.	1129	occur.
728		1130
729	=item * Erlang uses processes and a mailbox, AEMP does not queue.	1131	=item * Erlang uses processes and a mailbox, AEMP does not queue.
730		1132
731	Erlang uses processes that selectively receive messages, and therefore	1133	Erlang uses processes that selectively receive messages out of order, and
732	needs a queue. AEMP is event based, queuing messages would serve no	1134	therefore needs a queue. AEMP is event based, queuing messages would serve
733	useful purpose. For the same reason the pattern-matching abilities of	1135	no useful purpose. For the same reason the pattern-matching abilities
734	AnyEvent::MP are more limited, as there is little need to be able to	1136	of AnyEvent::MP are more limited, as there is little need to be able to
735	filter messages without dequeing them.	1137	filter messages without dequeuing them.
736		1138
737	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	1139	This is not a philosophical difference, but simply stems from AnyEvent::MP
		1140	being event-based, while Erlang is process-based.
		1141
		1142	You cna have a look at L<Coro::MP> for a more Erlang-like process model on
		1143	top of AEMP and Coro threads.
738		1144
739	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	1145	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
740		1146
741	Sending messages in Erlang is synchronous and blocks the process (and	1147	Sending messages in Erlang is synchronous and blocks the process until
		1148	a conenction has been established and the message sent (and so does not
742	so does not need a queue that can overflow). AEMP sends are immediate,	1149	need a queue that can overflow). AEMP sends return immediately, connection
743	connection establishment is handled in the background.	1150	establishment is handled in the background.
744		1151
745	=item * Erlang suffers from silent message loss, AEMP does not.	1152	=item * Erlang suffers from silent message loss, AEMP does not.
746		1153
747	Erlang makes few guarantees on messages delivery - messages can get lost	1154	Erlang implements few guarantees on messages delivery - messages can get
748	without any of the processes realising it (i.e. you send messages a, b,	1155	lost without any of the processes realising it (i.e. you send messages a,
749	and c, and the other side only receives messages a and c).	1156	b, and c, and the other side only receives messages a and c).
750		1157
751	AEMP guarantees correct ordering, and the guarantee that after one message	1158	AEMP guarantees (modulo hardware errors) correct ordering, and the
752	is lost, all following ones sent to the same port are lost as well, until	1159	guarantee that after one message is lost, all following ones sent to the
753	monitoring raises an error, so there are no silent "holes" in the message	1160	same port are lost as well, until monitoring raises an error, so there are
754	sequence.	1161	no silent "holes" in the message sequence.
		1162
		1163	If you want your software to be very reliable, you have to cope with
		1164	corrupted and even out-of-order messages in both Erlang and AEMP. AEMP
		1165	simply tries to work better in common error cases, such as when a network
		1166	link goes down.
755		1167
756	=item * Erlang can send messages to the wrong port, AEMP does not.	1168	=item * Erlang can send messages to the wrong port, AEMP does not.
757		1169
758	In Erlang it is quite likely that a node that restarts reuses a process ID	1170	In Erlang it is quite likely that a node that restarts reuses an Erlang
759	known to other nodes for a completely different process, causing messages	1171	process ID known to other nodes for a completely different process,
760	destined for that process to end up in an unrelated process.	1172	causing messages destined for that process to end up in an unrelated
		1173	process.
761		1174
762	AEMP never reuses port IDs, so old messages or old port IDs floating	1175	AEMP does not reuse port IDs, so old messages or old port IDs floating
763	around in the network will not be sent to an unrelated port.	1176	around in the network will not be sent to an unrelated port.
764		1177
765	=item * Erlang uses unprotected connections, AEMP uses secure	1178	=item * Erlang uses unprotected connections, AEMP uses secure
766	authentication and can use TLS.	1179	authentication and can use TLS.
767		1180
…		…
770		1183
771	=item * The AEMP protocol is optimised for both text-based and binary	1184	=item * The AEMP protocol is optimised for both text-based and binary
772	communications.	1185	communications.
773		1186
774	The AEMP protocol, unlike the Erlang protocol, supports both programming	1187	The AEMP protocol, unlike the Erlang protocol, supports both programming
775	language independent text-only protocols (good for debugging) and binary,	1188	language independent text-only protocols (good for debugging), and binary,
776	language-specific serialisers (e.g. Storable). By default, unless TLS is	1189	language-specific serialisers (e.g. Storable). By default, unless TLS is
777	used, the protocol is actually completely text-based.	1190	used, the protocol is actually completely text-based.
778		1191
779	It has also been carefully designed to be implementable in other languages	1192	It has also been carefully designed to be implementable in other languages
780	with a minimum of work while gracefully degrading functionality to make the	1193	with a minimum of work while gracefully degrading functionality to make the
781	protocol simple.	1194	protocol simple.
782		1195
783	=item * AEMP has more flexible monitoring options than Erlang.	1196	=item * AEMP has more flexible monitoring options than Erlang.
784		1197
785	In Erlang, you can chose to receive I<all> exit signals as messages	1198	In Erlang, you can chose to receive I<all> exit signals as messages or
786	or I<none>, there is no in-between, so monitoring single processes is	1199	I<none>, there is no in-between, so monitoring single Erlang processes is
787	difficult to implement. Monitoring in AEMP is more flexible than in	1200	difficult to implement.
788	Erlang, as one can choose between automatic kill, exit message or callback	1201
789	on a per-process basis.	1202	Monitoring in AEMP is more flexible than in Erlang, as one can choose
		1203	between automatic kill, exit message or callback on a per-port basis.
790		1204
791	=item * Erlang tries to hide remote/local connections, AEMP does not.	1205	=item * Erlang tries to hide remote/local connections, AEMP does not.
792		1206
793	Monitoring in Erlang is not an indicator of process death/crashes, in the	1207	Monitoring in Erlang is not an indicator of process death/crashes, in the
794	same way as linking is (except linking is unreliable in Erlang).	1208	same way as linking is (except linking is unreliable in Erlang).
…		…
816	overhead, as well as having to keep a proxy object everywhere.	1230	overhead, as well as having to keep a proxy object everywhere.
817		1231
818	Strings can easily be printed, easily serialised etc. and need no special	1232	Strings can easily be printed, easily serialised etc. and need no special
819	procedures to be "valid".	1233	procedures to be "valid".
820		1234
821	And as a result, a miniport consists of a single closure stored in a	1235	And as a result, a port with just a default receiver consists of a single
822	global hash - it can't become much cheaper.	1236	code reference stored in a global hash - it can't become much cheaper.
823		1237
824	=item Why favour JSON, why not a real serialising format such as Storable?	1238	=item Why favour JSON, why not a real serialising format such as Storable?
825		1239
826	In fact, any AnyEvent::MP node will happily accept Storable as framing	1240	In fact, any AnyEvent::MP node will happily accept Storable as framing
827	format, but currently there is no way to make a node use Storable by	1241	format, but currently there is no way to make a node use Storable by
…		…
837	Keeping your messages simple, concentrating on data structures rather than	1251	Keeping your messages simple, concentrating on data structures rather than
838	objects, will keep your messages clean, tidy and efficient.	1252	objects, will keep your messages clean, tidy and efficient.
839		1253
840	=back	1254	=back
841		1255
		1256	=head1 PORTING FROM AnyEvent::MP VERSION 1.X
		1257
		1258	AEMP version 2 has a few major incompatible changes compared to version 1:
		1259
		1260	=over 4
		1261
		1262	=item AnyEvent::MP::Global no longer has group management functions.
		1263
		1264	At least not officially - the grp_* functions are still exported and might
		1265	work, but they will be removed in some later release.
		1266
		1267	AnyEvent::MP now comes with a distributed database that is more
		1268	powerful. Its database families map closely to port groups, but the API
		1269	has changed (the functions are also now exported by AnyEvent::MP). Here is
		1270	a rough porting guide:
		1271
		1272	grp_reg $group, $port # old
		1273	db_reg $group, $port # new
		1274
		1275	$list = grp_get $group # old
		1276	db_keys $group, sub { my $list = shift } # new
		1277
		1278	grp_mon $group, $cb->(\@ports, $add, $del) # old
		1279	db_mon $group, $cb->(\%ports, $add, $change, $del) # new
		1280
		1281	C<grp_reg> is a no-brainer (just replace by C<db_reg>), but C<grp_get> is
		1282	no longer instant, because the local node might not have a copy of the
		1283	group. You can either modify your code to allow for a callback, or use
		1284	C<db_mon> to keep an updated copy of the group:
		1285
		1286	my $local_group_copy;
		1287	db_mon $group => sub { $local_group_copy = $_[0] };
		1288
		1289	# now "keys %$local_group_copy" always returns the most up-to-date
		1290	# list of ports in the group.
		1291
		1292	C<grp_mon> can be replaced by C<db_mon> with minor changes - C<db_mon>
		1293	passes a hash as first argument, and an extra C<$chg> argument that can be
		1294	ignored:
		1295
		1296	db_mon $group => sub {
		1297	my ($ports, $add, $chg, $lde) = @_;
		1298	$ports = [keys %$ports];
		1299
		1300	# now $ports, $add and $del are the same as
		1301	# were originally passed by grp_mon.
		1302	...
		1303	};
		1304
		1305	=item Nodes not longer connect to all other nodes.
		1306
		1307	In AEMP 1.x, every node automatically loads the L<AnyEvent::MP::Global>
		1308	module, which in turn would create connections to all other nodes in the
		1309	network (helped by the seed nodes).
		1310
		1311	In version 2.x, global nodes still connect to all other global nodes, but
		1312	other nodes don't - now every node either is a global node itself, or
		1313	attaches itself to another global node.
		1314
		1315	If a node isn't a global node itself, then it attaches itself to one
		1316	of its seed nodes. If that seed node isn't a global node yet, it will
		1317	automatically be upgraded to a global node.
		1318
		1319	So in many cases, nothing needs to be changed - one just has to make sure
		1320	that all seed nodes are meshed together with the other seed nodes (as with
		1321	AEMP 1.x), and other nodes specify them as seed nodes. This is most easily
		1322	achieved by specifying the same set of seed nodes for all nodes in the
		1323	network.
		1324
		1325	Not opening a connection to every other node is usually an advantage,
		1326	except when you need the lower latency of an already established
		1327	connection. To ensure a node establishes a connection to another node,
		1328	you can monitor the node port (C<mon $node, ...>), which will attempt to
		1329	create the connection (and notify you when the connection fails).
		1330
		1331	=item Listener-less nodes (nodes without binds) are gone.
		1332
		1333	And are not coming back, at least not in their old form. If no C<binds>
		1334	are specified for a node, AnyEvent::MP assumes a default of C<:>.
		1335
		1336	There are vague plans to implement some form of routing domains, which
		1337	might or might not bring back listener-less nodes, but don't count on it.
		1338
		1339	The fact that most connections are now optional somewhat mitigates this,
		1340	as a node can be effectively unreachable from the outside without any
		1341	problems, as long as it isn't a global node and only reaches out to other
		1342	nodes (as opposed to being contacted from other nodes).
		1343
		1344	=item $AnyEvent::MP::Kernel::WARN has gone.
		1345
		1346	AnyEvent has acquired a logging framework (L<AnyEvent::Log>), and AEMP now
		1347	uses this, and so should your programs.
		1348
		1349	Every module now documents what kinds of messages it generates, with
		1350	AnyEvent::MP acting as a catch all.
		1351
		1352	On the positive side, this means that instead of setting
		1353	C<PERL_ANYEVENT_MP_WARNLEVEL>, you can get away by setting C<AE_VERBOSE> -
		1354	much less to type.
		1355
		1356	=back
		1357
		1358	=head1 LOGGING
		1359
		1360	AnyEvent::MP does not normally log anything by itself, but sinc eit is the
		1361	root of the contetx hierarchy for AnyEvent::MP modules, it will receive
		1362	all log messages by submodules.
		1363
842	=head1 SEE ALSO	1364	=head1 SEE ALSO
843		1365
844	L<AnyEvent::MP::Intro> - a gentle introduction.	1366	L<AnyEvent::MP::Intro> - a gentle introduction.
845		1367
846	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.	1368	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
847		1369
848	L<AnyEvent::MP::Global> - network maintainance and port groups, to find	1370	L<AnyEvent::MP::Global> - network maintenance and port groups, to find
849	your applications.	1371	your applications.
		1372
		1373	L<AnyEvent::MP::DataConn> - establish data connections between nodes.
		1374
		1375	L<AnyEvent::MP::LogCatcher> - simple service to display log messages from
		1376	all nodes.
850		1377
851	L<AnyEvent>.	1378	L<AnyEvent>.
852		1379
853	=head1 AUTHOR	1380	=head1 AUTHOR
854		1381

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Comparing AnyEvent-MP/MP.pm (file contents): Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC vs. Revision 1.140 by root, Thu Mar 22 23:47:01 2012 UTC

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Revision 1.75 by root, Mon Aug 31 13:18:06 2009 UTC vs.
Revision 1.140 by root, Thu Mar 22 23:47:01 2012 UTC